Boyd's World-> Filing Cabinet-> Methods for Computing Smart Stats About the author, Boyd Nation

Methods for Computing Smart Stats

Yes, you too can roll your own smart stats. More usefully, you can use the descriptions below as jumping off points for creating your own versions, which is much more potentially interesting. As always, feel free to email if I've made something unclear -- I'm striving for a balance between readability and conciseness here.

AOPS (Adjusted On-Base Percentage plus Slugging Average)

• Using whatever park factors you prefer, for each team, compute the average team park factor (TPF) for the parks that they've played in. For neutral site games, just use a neutral park factor, which isn't accurate but won't matter that much. Normalize these values so that 1 is a neutral value.
• Using whatever method you prefer (I use average ISR adjusted for home field advantage), compute a strength of schedule (SoS) factor for each team. Again, normalize so that 1 is an average college schedule, whatever that is.
• For each player, compute OPS by adding OBP and SLG.
• For each player, compute AOPS by multiplying OPS by the SoS factor for his team and dividing by the TPF for his team.

RBOA (Runs below Opponent Average)

• Using whatever method you prefer (I use average ISR adjusted for home field advantage), compute a strength of schedule (SoS) factor for each team. Normalize so that 1 is an average college schedule, whatever that is.
• For each home park, find a park factor normalized to 1. For neutral sites, just use 1.
• For each team, compute a park-adjusted runs per game value. Do this by taking each game they've played, dividing the runs scored by the park factor for the park the game is played in, and averaging those values.
• For each pitcher, take each of his appearances and compute the expected runs allowed by taking the opponents' average adjusted runs per game and dividing it by the park factor for that site and then multiplying by the innings pitched divided by 9:

\$runs_expected = \$rpg{\$opponent} * \$pf{\$site} * \$ip / 9.0;

Subtract the actual runs allowed from that value to get RBOA for that game, and sum those values to get a season RBOA.

DERA (Defense-Independent Earned Run Average)

DERA is based on the notion that the pitcher has essentially no control over what happens to batted balls that stay in the park. The actual formula is context-dependent in the sense that it depends on the overall scoring rate in the game and on the varying rates of the Three True Outcomes; the one I'm using is back-correlated with Division I data from 2005. The formula is

```DERA = 3.93 + (-2.54 * SO + 4.13 * BB + 14.78 * HR) / IP;
```

There's a one inning per team game minimum required for listing on the leaderboard.

 Boyd's World-> Filing Cabinet-> Methods for Computing Smart Stats About the author, Boyd Nation